5'-Monohydroxyphylloquinone is the Dominant Naphthoquinone of PSI in the Green Alga Chlamydomonas reinhardtii
5'-Monohydroxyphylloquinone is the Dominant Naphthoquinone of PSI in the Green Alga Chlamydomonas reinhardtii
复制标题
DOI：
10.1093/pcp/pcr168
复制
发表时间：
2012-01-01
影响因子：
4.9
通讯作者：
Takahashi, Yuichiro
中科院分区：
文献类型：
--
作者：
Ozawa, Shin-ichiro;Kosugi, Makiko;Takahashi, Yuichiro
类囊体膜含有两种类型的醌，苯醌（质体醌）和萘醌，它们参与光合作用的电子传递。与苯醌不同，萘醌的化学种类（叶醌、甲基萘醌-4和5 '-单羟基叶醌）根据产氧光合生物而变化。以绿色衣藻为模式生物，研究了结合在PSI上的萘醌的功能。然而，在这种生物体中叶绿醌的水平和其他萘醌的存在仍然未知。在本研究中，我们发现5 '-单羟基叶绿醌是细胞和类囊体提取物中主要的萘醌，基于反相HPLC、吸收和质谱测量期间的保留时间。结果表明，与类囊体膜相比，PSI复合物中富集了2.5倍的5 '-单羟基叶绿醌，但在PSI缺陷型突变细胞中不存在。我们还在细胞和PSI复合物中发现了少量的叶绿醌，并估计积累的5 '-单羟基叶绿醌和叶绿醌分别占总萘醌含量的约90%和10%。这两个萘醌的比例保持几乎恒定的细胞和PSI复合物从对数和静止的细胞生长阶段。我们的结论是，5 '-单羟基叶绿醌和叶绿醌稳定共存的主要和次要萘醌衣原体PSI。
Thylakoid membranes contain two types of quinones, benzoquinone (plastoquinone) and naphthoquinone, which are involved in photosynthetic electron transfer. Unlike the benzoquinone, the chemical species of naphthoquinone present (phylloquinone, menaquinone-4 and 5'-monohydroxyphylloquinone) varies depending on the oxygenic photosynthetic organisms. The green alga Chlamydomonas reinhardtii has been used as a model organism to study the function of the naphthoquinone bound to PSI. However, the level of phylloquinone and the presence of other naphthoquinones in this organism remain unknown. In the present study, we found that 5'-monohydroxyphylloquinone is the predominant naphthoquinone in cell and thylakoid extracts based on the retention time during reverse phase HPLC, absorption and mass spectrometry measurements. It was shown that 5'-monohydroxyphylloquinone is enriched 2.5-fold in the PSI complex as compared with thylakoid membranes but that it is absent from PSI-deficient mutant cells. We also found a small amount of phylloquinone in the cells and in the PSI complex and estimated that accumulated 5'-monohydroxyphylloquinone and phylloquinone account for approximately 90 and 10%, respectively, of the total naphthoquinone content. The ratio of these two naphthoquinones remained nearly constant in the cells and in the PSI complexes from logarithmic and stationary cell growth stages. We conclude that both 5'-monohydroxyphylloquinone and phylloquinone stably co-exist as major and minor naphthoquinones in Chlamydomonas PSI.